In the technical field of liquid level sensors, two patent documents relevant to the present application which describe the prior art are listed herein. The first one is US Patent US2012/006060601 TETHERED FLOAT LIQUID LEVEL SENSOR, which describes a pulley-float device, in which, a float floats on a liquid level, a rotation sensor is used to record outputs, and a manner of transmitting data to a remote position is provided.
The second prior art document related to liquid level sensors is Blackburn's U.S. Pat. No. 5,410,913 ‘REMOTE INDICATING LIQUID LEVEL SENSOR’, which shows a set of magnetic sensors for detecting movement of a magnet on the top of a rotation shaft. A key innovation point of the present application is using a magnetic sensor to detect movement and using an electronic circuit to collect and transmit data.
In the technical field of rotation encoders, the applicant has applied for a Chinese patent application with Application Number of CN 201310040970.X and entitled ‘ABSOLUTE MAGNETIC ROTATION ENCODER’, which describes a novel rotation encoder, and in comparison to the existing encoder, its advantage lies in using a magnetic sensor instead of an optical sensor; the optical sensor is easy to get dirty and is also easy to fail. The construction, principle and advantages of the absolute magnetic rotation encoder have been described in detail and clearly in the above application of the applicant.
The liquid level sensing systems in the prior art have some defects. They provide electronic output signals, but visual inspection cannot be carried out. The encoders are based on optics, and the optical encoders are prone to failure as a result of getting dirty. At present, there is no method that can be applied to make these devices widely applicable to measuring liquid levels in a well, and there is no method for improving the precision of this type of liquid level measurement.